NASA | Developing a Comet Harpoon for Sample Return

Uploaded by NASAexplorer on 13.12.2011

Since the beginning of the
space age NASA has explored our solar system, bringing back
unprecedented scientific knowledge, but only a handful of missions
over the past 50 years have actually collected and returned samples
from these far off places. Astronauts
on the Apollo program traveled to our Moon, bringing back over 800 lbs
of moon rock. Stardust was an unmanned mission that collected samples
from the coma of comet Wild 2 before returning them to Earth for in-depth
scientific study. OSIRIS-Rex is the most recently funded
sample return mission that will launch in 2016 and return surface
samples from an asteroid in 2023.
The Comet Nucleus Sample Return mission will collect subsurface samples
from a comet and return them to Earth. Comets and Asteroids are
leftover remnants from the early solar system and by studying samples from these
objects, we can learn more about the formation of our solar system and
may find clues to the origin of life on Earth. Collecting a sample
from a comet is a challenging feat for many reasons, including how far
away they are from Earth and how little gravity they provide. In our
concept, harpoons are used to collect and retrieve samples from interesting locations
on these exotic objects. Traditionally,
when collecting samples on Earth, we use scoops, shovels, or coring drills,
but on comets and asteroids there is so little gravity that you would
push yourself off the surface if you used one of these methods. Harpoons allow
you to grapple to the surface while taking a sample, allowing rapid sample collection
and retrieval. First, we choose a specific interesting
area to take a sample from and then fire a sample collecting harpoon into that
spot. As the harpoon penetrates into the comet, it fills its inner sample
cartridge with subsurface material as it goes deeper. When it reaches its
maximum depth the sample cartridge closure mechanism shuts, trapping all
the material inside it. The sample cartridge is then with drawn from the outer harpoon
sheath and pulled back into the space craft. The sample is
then brought back to a terrestrial laboratory where scientists examine the collected
samples in a pristine environment.
Before we journey here, we need to work here
in the lab, studying comet and asteroid analogs.
In order to determine how much energy is required to penetrate different depths
in various density material, we’ve designed and built a harpoon
test laboratory. Although the actual mission will use a cannon,
for safety reasons, we’ve employed a ballista to fire the harpoons.
By correlating the imparted energy versus the penetration depth, we will
know how to size the explosive charge for the actual mission.
The harpoon lab also allows us to study how the tip geometry, cross
section and mass of the harpoon affect its penetration.
This has allowed us to optimize the harpoon sheath for a range of
possible comet densities. Although sample return missions can be quite
costly and complex, they offer important advantages over missions
that study their subjects from a distance. Sample return missions allow
terrestrial laboratories to study in far greater detail, with a variety
of techniques, and can even be studied by future generations with
technologies that have not been invented yet.